Just like the dreadnought, the flattop steel-string guitars in the 0, 00, and 000 formats were originally developed and built by Martin and later adopted as standards by other manufacturers. In general, these instruments are known as Concert (0), Grand Concert (00), and Auditorium (000).
Guitars in the size 0 were introduced by Martin in the mid-19th century and were among the largest instruments on the market at that time. The guitars had a width of approximately 34.4 cm and a length of approximately 48.5 cm, making them relatively small by today's standards. However, in the 1920s and 1930s, these instruments became very popular, and guitars in the "0 size" were available from numerous manufacturers. Today, there are very few companies that produce guitars in the "0" size. Nevertheless, these instruments have their admirers. Their very clean, booming-free sound is highly sought after by studio musicians. Volume is not the main concern here, allowing the "smaller" guitars to showcase their tonal advantages optimally.
To meet the demand for increasing volume, Martin introduced the 00 in 1871 (width 36 cm, length 53.3 cm). This instrument serves as the basis for many modern guitar designs. Since these instruments offer an optimal compromise between acoustic qualities and feedback resistance, many manufacturers use the 00 dimensions as a starting point for their electro-acoustic designs.
Finally, we have the Triple 0 (000). This guitar has a body width of approximately 38 cm and represents an optimal compromise between volume, sound density, and playing comfort. It is no wonder that Eric Clapton values his Martin 000 above all else and uses the guitar both in the studio and on stage for his tasteful fingerstyle accompaniments and soulful solos. Therefore, it is not surprising that the 000 has served as the inspiration for many modern instruments in the auditorium style. With a smaller body, superb handling (especially suitable for guitarists with smaller hands due to the shorter scale length), and an absolutely precise tone, it is the perfect instrument for cool fingerpicking and hot solos.